Noninvasive assessment of fetal cardiac electrophysiology has not been routinely possible despite many decades of fetal ECG research. Recently, however, we and other groups have demonstrated the efficacy of fetal magnetocardiography (fMCG), the magnetic analog of fetal ECG, as an effective new method of assessing fetal heart rate, rhythm, and conduction. The long-term goal of this program is to develop fMCG as a new technology for fetal investigation and clinical application. If successful, this research can improve the diagnosis of life-threatening forms of fetal arrhythmia and shed light on causes of unexplained fetal death. It can also provide an effective means of monitoring the effects of fetal therapies and can aid in the evaluation of new therapies. The short-term objective of the research proposed here is to extend the functionality of fMCG by combining it with other techniques and to perform further patient studies to increase the base of scientific knowledge in the nascent field of fetal cardiac electrophysiology. The specific aims are as follows: 1. Develop and apply detectors based on statistical estimation and detection theory to identify repolarization abnormalities, such as QTc prolongation and T-wave alternans. 2. Develop and apply methodology for analysis of simultaneous fMCG/echocardiography recordings in order to directly compare fetal electrical and mechanical rhythm and evaluate fetal electromechanical function. 3. Combine fetal actocardiography with ultrasound surveillance in order to improve the assessment of fetal well-being. 4. Continue our studies of normal pregnancies and pregnancies complicated by fetal arrhythmia and other high-risk conditions, incorporating techniques developed in the preceding aims.